Mortality Associated With Acute Respiratory Distress Syndrome 2009-2019: A Systematic Review and Meta-regression 

Abstract Background: Acute respiratory distress syndrome (ARDS) is a common occurrence in an intensive care unit. The reported mortality in studies evaluating acute respiratory distress syndrome is highly variable. The adherence to ventilatory specific and adjunctive therapies is also highly variable. We investigated the mortality of ARDS since the 2009 H1N1 pandemic and examined the adherence to ventilatory specific and adjunctive therapies.Methods: We performed a systematic search in MEDLINE and EMBASE using a highly sensitive criterion from January 2009 to May 2019. We then ran a proportional meta-analysis for mortality and a meta-regression analysis using certain variables to address heterogeneity. Results: We screened 5361 citations, of which 85 fully met inclusion criteria. The weighted pooled mortality of all 85 studies published from 2009 to 2019 was 38% (95% CI 35,40). Mortality was higher in observational studies [40% (95% CI 37, 42)] compared to RCTs [35% (95% CI 30,39)], (p=0.04) Significant variability exists in literature of reported tidal volumes, positive end expiratory pressures, plateau pressures, and use adjunctive therapies. The tidal volumes in our systematic review ranged from 5.8 to 8.9 ml/kg with a mean of 7.2 ml/kg. PEEP ranged from 4.6 to 16.1 cm H2O at the time of enrollment with a mean of 10.2 cm H2O. Reported plateau pressures ranged from 21.0 to 35.1 cm H2O, with a mean of 25.6 cm H2O. Higher reported initial PaO2/FiO2 ratios were associated with decreased mortality. A trend towards decreased mortality was seen with lower reported tidal volumes in the included studies.Conclusions: Over the last decade, the mortality in ARDS has marginally improved and there exists significant heterogeneity in the utilization of low tidal volume strategies, application of PEEP and the adoption of adjunctive therapies in the management of these patients in published literature.